Investigation of Genetic and Epigenetic Factors in the Molecular Pathogenesis of Hereditary Angioedema Patients Without SERPING1 Mutation

Project no. 21840 · Status: Kapanmış (Yayın bekleniyor) · 2020

Summary

Hereditary Angioedema (HAE) is a rare, autosomal dominant disorder characterized by recurrent and potentially life-threatening angioedema attacks. The disease is primarily caused by mutations in the SERPING1 gene, which result in either insufficient production of the C1INH protein (Type I HAE-C1INH) or production of a dysfunctional protein (Type II HAE-C1INH). Additionally, another form of HAE (HAE-nC1INH) exists, where patients exhibit normal C1INH protein levels and function. This form is associated with mutations in genes such as F12, PLG, ANGPT1, KNG1, MYOF, and HS3ST6, each classified into distinct subtypes. Moreover, cases with low C1INH levels and function but without SERPING1 mutations have also been reported in the literature.In this study, we hypothesized that alternative gene mutations could contribute to the molecular pathology of Type I HAE-C1INH cases without a detectable SERPING1 mutation. Accordingly, whole-exome sequencing was performed on five patients with Type I HAE-C1INH who lacked SERPING1 mutations to identify gene variants potentially contributing to disease pathology. Peripheral blood samples were collected from these patients for genomic DNA isolation, followed by next-generation sequencing. Raw data were analyzed by mapping to the reference human genome GRCh38 using CLC Genomics Workbench 20.0.4. Variants identified were categorized based on comparison with the ClinVar and dbSNP databases: those listed in ClinVar, those found only in dbSNP, and those unlisted in both databases. To assess variant significance, VarSome and Franklin databases were utilized. Novel SERPING1 variants, not previously reported in ClinVar or dbSNP, were identified in two patients. The heterozygous c.-22-2A>G variant detected in the first patient was documented for the first time in the Turkish population, and the c.826_832del p.Arg276* variant in the second patient was also newly identified. Familial linkage was confirmed through high-resolution melting analysis (HRM) and Sanger sequencing.In epigenetic evaluations, quantitative reverse transcription PCR (qRT-PCR) was used to investigate epigenetic changes and assess the expression profile of SERPING1/C1INH. In patients with Type I HAE-C1INH who did not carry SERPING1 mutations, SERPING1 mRNA expression levels were significantly lower compared to those of family members, suggesting that epigenetic or environmental factors may suppress gene expression, impacting disease phenotype.At the protein level, a significant correlation was observed between serum and monocyte C1INH protein levels in the Classic Type I HAE-C1INH group (R²=0.5231, p<0.0001), whereas no significant correlation was found between these parameters in the Type II HAE-C1INH group (R²=0.1052, p<0.804), indicating potentially distinct regulatory mechanisms in Type I and Type II HAE-C1INH.Moreover, miRNA and lncRNA expression profiling analyses were performed, examining 85 miRNAs and 85 lncRNAs. In both Classic Type I and Type II HAE-C1INH groups, expression levels of miRNAs such as hsa-miR-125b-5p, hsa-mir-335-5p, and hsa-miR-146a-5p were decreased, while increases were observed in hsa-mir-23a-5p and hsa-let-7a-5p. In the Classic Type I HAE-C1INH group, significant decreases were noted in lncRNAs such as MALAT1, HOTAIR, MEG3, and NEAT1, whereas in the Type II HAE-C1INH group, these same lncRNAs displayed increased expression. These findings suggest that miRNAs and lncRNAs may play distinct regulatory roles in both HAE types. Further transcriptomic analyses and studies on C1INH interactions with RNA molecules or other proteins are warranted to elucidate the molecular pathology of HAE cases without SERPING1 mutations.

View details